the reason airplanes need speed is basically because their propeller/jet blades are too small to be efficient at slow speed. You need a certain amount of force to lift off, and the more air you push off of at once the more force you get per energy. The airplanes go sideways so that their wings, which are very big, can provide the lift instead of their engines. Also this means that if you want to go fast and hover efficiently, you need multiple mechanisms because the low volume high speed engine won’t also be efficient at low speed
the reason airplanes need speed is basically because their propeller/jet blades are too small to be efficient at slow speed. You need a certain amount of force to lift off, and the more air you push off of at once the more force you get per energy. The airplanes go sideways so that their wings, which are very big, can provide the lift instead of their engines. Also this means that if you want to go fast and hover efficiently, you need multiple mechanisms because the low volume high speed engine won’t also be efficient at low speed